
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>用键盘控制DIV</title>
<style type="text/css">
html,body{overflow:hidden;}
body{margin:0;padding:0;}
pre{color:green;padding:10px 15px;background:#f0f0f0;border:1px dotted #333;font:12px/1.5 Courier New;margin:12px;}
span{color:#999;}
#box{position:absolute;top:50px;left:300px;width:100px;height:100px;background:red;}
</style>
<script type="text/javascript">
window.onload = function ()
{
	var oBox = document.getElementById("box");
	//利用状态值的变化，控制功能的选择
	var bLeft = bTop = bRight = bBottom = bCtrlKey = false;
	
	setInterval(function ()
	{
		if (bLeft)
		{
			oBox.style.left = oBox.offsetLeft - 10 + "px"
		}
		else if (bRight)
		{
			oBox.style.left = oBox.offsetLeft + 10 + "px"
		}
		
		if (bTop)
		{
			oBox.style.top = oBox.offsetTop - 10 + "px"	
		}
		else if(bBottom)
		{
			oBox.style.top = oBox.offsetTop + 10 + "px"
		}
		//防止溢出
		limit();
	},30);	
	
	document.onkeydown = function (event)
	{
		var event = event || window.event;
		bCtrlKey = event.ctrlKey;
		
		switch (event.keyCode)
		{
			case 37:
				bLeft = true;
				break;
			case 38:
				if(bCtrlKey)
				{
					var oldWidth = oBox.offsetWidth;
					var oldHeight = oBox.offsetHeight;
					
					oBox.style.width = oBox.offsetWidth * 1.5 + "px";
					oBox.style.height = oBox.offsetHeight * 1.5 + "px";				
					
					oBox.style.left = oBox.offsetLeft - (oBox.offsetWidth - oldWidth) / 2 + "px";
					oBox.style.top = oBox.offsetTop - (oBox.offsetHeight - oldHeight) / 2 + "px";
					
					break;	
				}
				bTop = true;
				break;
			case 39:
				bRight = true;
				break;
			case 40:
				if(bCtrlKey)
				{
					var oldWidth = oBox.offsetWidth;
					var oldHeight = oBox.offsetHeight;
					
					oBox.style.width = oBox.offsetWidth * 0.75 + "px";
					oBox.style.height = oBox.offsetHeight * 0.75 + "px";				
					
					oBox.style.left = oBox.offsetLeft - (oBox.offsetWidth - oldWidth) / 2 + "px";
					oBox.style.top = oBox.offsetTop - (oBox.offsetHeight - oldHeight) / 2 + "px";
					
					break;	
				}
				bBottom = true;
				break;
			case 49:
				bCtrlKey && (oBox.style.background = "green");
				break;
			case 50:
				bCtrlKey && (oBox.style.background = "yellow");
				break;
			case 51:
				bCtrlKey && (oBox.style.background = "blue");
				break;
		}
		
		return false
	};

	document.onkeyup = function (event)
	{
		switch ((event || window.event).keyCode)
		{
			case 37:
				bLeft = false;
				break;
			case 38:
				bTop = false;
				break;
			case 39:
				bRight = false;
				break;
			case 40:
				bBottom = false;
				break;
		}
	};

	//防止溢出
	function limit()
	{
		var doc = [document.documentElement.clientWidth, document.documentElement.clientHeight]
		//防止左侧溢出
		oBox.offsetLeft <=0 && (oBox.style.left = 0);
		//防止顶部溢出
		oBox.offsetTop <=0 && (oBox.style.top = 0);
		//防止右侧溢出
		doc[0] - oBox.offsetLeft - oBox.offsetWidth <= 0 && (oBox.style.left = doc[0] - oBox.offsetWidth + "px");
		//防止底部溢出
		doc[1] - oBox.offsetTop - oBox.offsetHeight <= 0 && (oBox.style.top = doc[1] - oBox.offsetHeight + "px")
	}
};
</script>
</head>
<body>
<pre>
红色方块为键盘操作区域，您可以进行如下操作：

上：↑ 下：↓ 左：← 右：→

Ctrl + 1 : 背景变为绿色
Ctrl + 2 : 背景变为黄色
Ctrl + 3 : 背景变为蓝色
Ctrl + ↑ : 放大
Ctrl + ↓ : 缩小
</pre>
<div id="box"></div>
</body>
</html>
